"A trigger point is a spot or a point in a muscle that refers a sensation to another area of the body. The sensation could be:
A latent trigger point is one that is not actively creating a pain pattern. The pain is either intermittent or not present until the trigger point itself is directly pressed or activated by some activity.
An active trigger point is one that is actively creating pain or another sensation in your body. In other words, if a trigger point was referring pain to your arm, you would be walking around with pain in your arm on a regular basis.
What Causes Trigger Points to Form?
- Blunt trauma – such as a car accident or a fall.
- Overuse – perhaps a muscle working too hard by compensating for other muscles.
- Lack of use – muscle dysfunction and a decrease in lack of blood flow can be due to lack of use. This can lead to the formation of trigger points.
Not to get too technical but… we are talking about dysfunction on the cellular level. A small number of muscle cells remain in a state of contraction when a trigger point exists. Why? This usually occurs because the calcium used to change the charge inside the cell, which causes the contraction to happen, is not removed or neutralized. As a result the cells stay in a state of contraction.
This forms a small bolus or a tiny “knot” in the muscle at a cellular level. It’s not that the entire muscle is in a state of contraction, just “X” number of muscles cells."
Read more at http://www.yoganatomy.com/2014/01/trigger-points/?utm_source=YogAnatomy+Newsletter&utm_campaign=790f150713-email_02_2014&utm_medium=email&utm_term=0_452e96d3c5-790f150713-97124881